Datasheet
MAX31725/MAX31726
±0.5°C Local Temperature Sensors
10Maxim Integrated
Internal Registers
The device contains four registers, each of which consists
of 2 bytes. The configuration register contains only 1
byte of actual data and, when read as a 2-byte register,
repeats the same data for the second byte. During a
2-byte write to the configuration register the second
byte written takes precedence. The device’s pointer
register selects between the four data registers shown
in Table 2. During reads and writes the pointer register
auto increments after every 2 data bytes, but does not
wrap from address 03h-00h. The pointer register must
be written for each I
2
C transaction. All registers are read
and write, except for the read-only temperature register.
Write to the configuration register by writing the slave
address byte, the pointer register byte to value 01h, and
a data byte. The T
OS
and T
HYST
registers require the
slave address byte, pointer register byte, and 2 data
bytes. If only 1 data byte is written, it is saved in bits
D[15:8] of the respective register. If more than 2 data
bytes are written, the pointer register auto increments
and if pointing to a valid address, additional data writes
to the next address. See Figure 3.
Table 2. Register Functions and POR State
Figure 3. I
2
C-Compatible Timing Diagram (Write)
REGISTER
NAME
ADDRESS
(Hex)
POR STATE
POR STATE
(°C)
READ/
WRITE
Hex BINARY
Temperature 00 0000h 0000 0000 0000 0000 0 Read-only
Configuration
MAX31725
01 00h 0000 0000 — R/W
Configuration
MAX31726
01 40h 0100 0000 — R/W
T
HYST
02 4B00h 0100 1011 0000 0000 75 R/W
T
OS
03 5000h 0101 0000 0000 0000 80 R/W
ADDRESS
BYTE
ADDRESS
BYTE
(a) CONFIGURATION REGISTER WRITE.
(b) T
OS
AND T
HYST
WRITE.
POINTER
BYTE
POINTER
BYTE
MOST SIGNIFICANT
DATA BYTE
LEAST SIGNIFICANT
DATA BYTE
CONFIGURATION
BYTE
ACK BY
MAX31725/
MAX31726
ACK BY
MAX31725/
MAX31726
ACK BY
MAX31725/
MAX31726
ACK BY
MAX31725/
MAX31726
ACK BY
MAX31725/
MAX31726
START
BY
MASTER
START
BY
MASTER
ACK BY
MAX31725/
MAX31726
ACK BY
MAX31725/
MAX31726
STOP
COND BY
MASTER
STOP
COND BY
MASTER
D1 D010 D3*D4*D5* D2* D1* R/W 000000
D0D1D2D3D4D5D6D7
D0D1D0D1 D2D3D4D5D6D7
D0D1D2D3D4D5D6D7
10 000000D3*D4*D5* D2* D1* R/W
111199
99
111999
*SEE TABLE 1A.